Author profile comments system

Comments are bound to post IDs. So you need a post ID for each user.

Register a custom post type, make it not public and create one hidden post for each user. Store the ID in an user-meta field.
Now assign the comments to that post’s ID. Do not use comments_template(). That’s an ugly monster, dealing with globals and way too complex to hack around. Fetch the comments with get_comments() instead.

The print the comment form, add a hidden field for author archive URL, hook into comment_post_redirect and send the commenter back correctly.